yacc

When there is a shift/reduce conflict in Yacc/Bison, is it possible to force the conflict to be solved exactly as you want? In other words: is it possible explicitly force it to prioritize the shift or the reduce? For what I have read, if you are happy with the default resolution you can tell the generator to not complain about it . I really don't like this because it is obfuscating your rational choice. Another option is to rewrite the grammar to fix the issue. I don't know if this is always possible and often this makes it much harder to understand. Finally, I have read the precedence rules

I am using Python with PLY to parse LISP-like S-Expressions and when parsing a function call there can be zero or more arguments. How can I put this into the yacc code. This is my function so far: def p_EXPR(p): '''EXPR : NUMBER | STRING | LPAREN funcname [EXPR] RPAREN''' if len(p) == 2: p[0] = p[1] else: p[0] = ("Call", p[2], p[3:-1]) I need to replace "[EXPR]" with something that allows zero or more EXPR's. How can I do this? How about this: EXPR : NUMBER | STRING | LPAREN funcname EXPR_REPEAT RPAREN EXPR_REPEAT: /*nothing*/ | EXPR EXPR_REPEAT Are you sure you want a Context Free Grammar and

I'm trying to write my first parser with Flex & Bison. When parsing numbers, I'm trying to save their values into the yylval structure. The problem is, yylval is null when the lexer reaches a number, which causes a segmentation fault. (Related point of confusion: why is it that in most Flex examples (e.g. here ), yylval is a structure, rather than a pointer to a structure? I couldn't get yylval to be recognized in test.l without %option bison-bridge , and that option made yylval a pointer. Also, I tried initializing yylval in main of test.y, but yylval = malloc(...) gives a type mismatch-- as

I'm writing a grammar for parsing a computer language, that can be used with Parse::Eyapp . This is a Perl package that simplifies writing parsers for regular languages. It is similar to yacc and other LALR parser generators, but has some useful extensions, like defining tokens in terms of regular expressions. The language I want to parse uses keywords to denote sections and describe control flow. It also supports identifiers that serve as placeholders for data. An identifier can never have the same name as a keyword. Now, here comes the tricky part: I need to separate keywords from

I am trying to run an example I found online of a calculator. But I have this error showing every time I run my gcc command. Here are the commands that I run: flex -l calc3.l yacc -vd calc3.y gcc y.tab.c -lm -ll -> at this point I got this error message: /tmp/ccPOq58f.o : In function 'yyparse': y.tab.c: undefined reference to 'yylex' collect2: error: ld returned 1 exit status Here is my code: calc3.l %{ #include <stdlib.h> #include "calc3.h" #include "y.tab.h" void yyerror(char *); %} %% [a-z] { yylval.sIndex = *yytext - 'a'; return VARIABLE; } 0 { yylval.iValue = atoi(yytext); return INTEGER;

What is the best way to handle multiple Flex/Bison parsers inside a project? I wrote a parser and now I need a second one in the same project. So far in the third section of parser1.y I inserted the main(..) method and called yyparse from there. What I want to obtain is having two different parsers ( parser1.y and parser2.y ) and be able to use them from an external function (let's assume main in main.cpp ). Which precautions should I use to export yyparse functions outside .y files and how should I handle two parsers? PS. I'm using g++ to compile but not the C++ versions of Flex and Bison and